The Neuroepidemiology Program Project supports a core portion which represents the diagnostic and procedural indices collected from existing medical records for the population of Olmsted County, Minnesota. This automated and computerized data base supports a variety of epidemiologic projects conducted by Mayo staff, residents, students and visiting scientists. The specific aims of the core are: 1) to continuously update the Mayo and non-Mayo sources of diagnostic information, and 2) to provide a resource that can be used by qualified scientific researchers from both inside and outside the institution. The data base will be used to provide identification of appropriate cases of disease for epidemiologic studies. The constant updating of the index will ensure the availability of data which provide population-based estimates of disease occurrence and long-term trends for each of the projects supported by this grant. During year four, we expect completion or continuation of the studies on lumbar and lumbosacral disc surgery, carpal tunnel syndrome, and mental retardation; a case-control study of risk factors for brain tumors will also begin.